Optical imaging system

ABSTRACT

An optical imaging system for image exposing a static image on a photosensitive plate comprising scanning means for progressively scanning the static object at a first speed with a light source; means for moving a first mirror in parallel in the same direction as the scanning means at a second speed, the plane containing the first mirror being inclined with respect to the plane containing the static image; means for moving a second mirror in parallel in the same direction as the first mirror at a third speed, the second mirror facing the first mirror, the plane containing the second mirror being inclined with respect to the plane containing the static image so that the optical length along the path defined by the scanning means, first mirror and second mirror is substantially constant at all points during the movement of the scanning means, first mirror and second mirror; means for optically focusing the image reflected from the second mirror onto the photosensitive plate; means for moving the photosensitive plate at a speed relative to the scanning means whereby the imaging system can be compactly arranged because the plane containing the second mirror is inclinded to the plane containing the static image.

United Sta OPTICAL IMAGING SYSTEM [75] Inventor:

[73] Assignee: Fuji Shashin Koki Kabushiki Kaisha, Omiya-shi, Saitama,Japan [22] Filed: Mar. 29, 1972 [21] Appl. No.1 239,139

Noboru lki, Omiya City, Japan [30] Foreign Application Priority DataPrimary Examiner-John M. Horan Attorney-Addams and Ferguson ABSTRACT Anoptical imaging system for image exposing a static EARCH ROOM Dec. 11,1973 image on a photosensitive plate comprising scanning means forprogressively scanning the static object at a first speed with a lightsource; means for moving a first mirror in parallel in the samedirection as the scanning means at a second speed, the plane containingthe first mirror being inclined with respect to the plane containing thestatic image; means for moving a second mirror in parallel in the samedirection as the first mirror at a third speed, the second mirror facingthe first mirror, the plane containing the second mirror being inclinedwith respect to the plane containing the static image so that theoptical length along the path defined by the scanning means, firstmirror and second mirror is substantially constant at all points duringthe movement of the scanning means, first mirror and second mirror;means for optically focusing the image reflected from the second mirroronto the photosensitive plate; means for moving the photosensitive plateat a speed relative to the scanning means whereby the imaging system canbe compactly arranged because the plane containing the second mirror isinclinded to the plane containing the static image.

1 Claim, 3 Drawing Figures OPTICAL IMAGING SYSTEM BACKGROUND OF THEINVENTION 1. Field of the Invention This invention relates to an opticalimaging system including a slit exposure device for scanriing a staticob ject. More precisely, this invention relates to an exposure devicefor use in a copying machine wherein a static object is scanned usingmirrors to obtain magnified, reduced, SFaCtGaI" siie copies which can beobtained from either a manuscript sheet or a bulky book, the photo-imagebeing focused on a moving sensitive plate via a projection lens.

2. Description of the Prior Art In conventional optical systems forscanning static objects, scanning is performed by fixed lens andmirrors. However, compact arrangement of the system is very difficult. V

There have been attempts to avoid this problem, as disclosed in JapanesePatent Publication No. 6647/1964. The system disclosed in the Japanesepublication comprises a fixed lens a, and parallel moving mirrors 1; andc which move in the direction of the arrow A, as shown in FIG. 1. Mirrorb (together with the light source above it) moves at a speed equal tothat.

of the sensitive plate e, the latter moving in the direc tion of thearrow B. The mirror b scans a static or non moving object d. The speedof the mirror 0 is one-half of that of mirror b, so that optical lengthin the system iis kept constant. However, the mirror 0 and thesensiifttive plate e are perpendicularly disposed with respect gto eachother. Thus, since the incidence angle at mirror is equal to thereflection angle therefrom whereby the direction of the reflection tendsdownward rather sharply, the distance between the object d and saidplate e is too long to permit a sufficiently compact arrangement of theoptical system.

Summary of the Invention Thus, an object of this invention is to providea compact optical system wherein the position of the second mirror(corresponding to mirror c of FIG. I) is not perpendicular to the objectbut inclined to some extent thereto so that the slope of the reflectiontherefrom becomes comparatively gentle whereby the distance between theobject and plate becomes relatively short when compared to that of theconventional system of FIG. 1. Further, the system is characterized inthat the ratio of the parallel moving speeds of the light source and thefirst and second mirrors b and c is not limited to ltlz r, as in theprior art, but rather is defined by a trigonometrical function ratio,whereby the optical length in the system is kept constant.

Other objects and advantages of this invention will become apparent uponreading the appended claims in conjunction with the following detaileddescription and the attached drawing. 7

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a diagram showingfundamentals of conventional scanning optical system.

FIG. 2 is a diagram showing fundamentals of an embodiment of thescanning optical system according to this invention.

FIG. 3 is a diagram showing fundamentals of another embodiment of thesame system according to this invention, where I is,-an object to becopied, 2 a lighting device, 3 a first mirror, 4 a second mirror, 5 afixed lens, 6 a fixed mirror, and 8 a sensitive plate.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring to FIG. 2, the reflectionimage of an object 1 exposed by a light source or scanner 2 is focusedon a moving sensitive plate 8 via a fixed lens 5, a fixe d mirror 6, andslit 7 after successive reflections by a first "mirror 3 moving inparallel to object I and a second mirror 4 moving inparallel at a speedrelated to that of mirror 3. The procedure for obtaining the relationbetween speeds of mirrors 3 and 4 will be now described.

Assume that the angles between the normal lines of mirrors 3 and 4 andthe longitudinal axis are 6, and 6 respectively. Further, assume thatthe initial optical axis point of object 1 is A, that of mirror 3 is B,that of mirror 4 is C, that of fixed mirror 6 is D, and those of object1, mirror 3, and said mirror 4 are A, E, and F respectively afterscanning of the optical axis of object 1. The relation E+FC=Z E+EF+IT 1must be established between the moved distance, S of lighting source 2,S, of mirror 3, and S of mirror 4 in order to keep the optical lengthconstant before, after, and during scanning.

Assume that a line is drawn in parallel to EC from E to form the lineEGwhereby GCFE forms a parallelogram, where EF=Gc,andF c=E6. As H Z7,where I is the intersection of the extension of BB and TE, Eq. I can bewritten as 176 TE F5 (2) realizing that TE A7? [Tand C= G+ GE.Therefore, optical lengths before and after scanning can be keptconstant if the relation,

TE-+ FIG 1 2') Where 1% l, is satisfied. It can be shown that TE (S -8tan (1r-0,) E1? s,/s-in2 0,0, Hence, Eq. 2' can be converted to 0 1) I)z/ z) (3) Assuming that the intersection of the perpendicular line drawnthrough G and ITTis J, and the intersection of the line parallel to ETdrawn through E and GT is H,

e o S2 1 SI Hence,

S S =Isin (2 0,-rr) 4 As GJ GT1 ET,

1 cos (2 6,-1r) S cot2(0,6,)=(S -S,)tan(1r-6,)

(5) So that, from Eqs. 3, 4, and 5 S 1 sin (2 0,-11) S,

S I SIlI 61 I' S: SIII2(01 62) Sg/tan('n' 0 i z)] I By eliminating S,from above equations,

S 2 cot (Hr-6 cosl) [ltan 0, tan(0,-0,)]

[sin (6,6,)cos26, cos6,]/[tan 6, sin (0, Therefore,

S S, S, 1 tan 6, tan (0,6,):

Accordingly, if the lighting device 2, the mirror 3, and the mirror 4move in parallel at relative speeds which fulfill the abovetrigonometrical relation, the optical length can be kept constant andthe copied image from the original will be focused on the sensitive plae8 via lens and fixed mirror 6.

For example,

5, 0.59591 when 0, 120 and 0, 80. Thus,

8,, S, S l 0.844 0.408.

Therefore, when light source or scanner 2 moves at the same speed v asthat of the sensitive plate 8, and the first mirror 3 and the secondmirror 4 move in parallel at the speeds 0.844v and 0.408v respectively,the optical length is kept constant and an actual size copy of theoriginal is focused on plate 8. Means for moving the scanner 2, themirrors 3 and 4, and plate 8 are diagrammatically indicated at 9, m, n,0 and p and may be any means known to those of ordinary skill in theart.

Similarly, as shown in FIG. 3.

S, 0.4196 1 when 0, 120 and 0, 70.

Thus,

Therefore, when said light source or scanner 2 moves at the same speed vas that of plate 8, and mirrors 3 and 4 move in parallel at the speeds0.7422v and 0.3263v respectively, the optical length is kept constantand an actual size copy of the original is focused on the plate 8. Inthis case, as the reflection from said mirror 4 is reflected upwardswith respect to horizontal plane, whole optical system becomes much morecompact.

Further, if 0, 120 and 0 90", mirror 4 is perpendicular to the scanningplane, the following relationships hold:

5 \TI S1 S2 V 3/2 I And,

Accordingly, when the scanner moves at the same speed as that of thesensitive plate, and the first mirror and second mirror move in parallelat the speeds v and 5 1v respectively, the optical length is keptconstant. This relation is essentially equivalent to the relation in thepreviously mentioned Japanese Patent Publication shown in FIG. 1.

According to this invention, as mentioned above, when the lightingdevice, the first mirror, and the second mirror move respectively atarbitrary speeds which are determined by the aforementionedtrigonometrical speed ratio, the optical length can be kept constant andthe copied image from the original can be focused on the sensitiveplate. In other words, according to this invention, by suitably varyingthe angles 6, and 6 of the first and the second mirrors, wide selectionof moving speed ratios of the lighting device and the mirrors ispossible whereby the whole optical system can be much more compact thanthat of the prior art. Furthermore, in the optical system according tothis invention, the first mirror 3 functions not only as a scanningmirror but also as a optical length correction mirror together with thesecond mirror 4, while the first mirror I; in the prior art as shown inFIG. 1 functions only as a scanning mirror, the correction of theoptical length being exclusively performed by the second mirror c.

Thus, this invention makes it possible to produce a simple and compactcopying machine in which copies of desired size, magnified, reduced, andactual size, can be focused on a moving plate from the original, whichmay be either a manuscript sheet or a bulky book, via mirrors and lens.

Numerous modifications of the invention will become apparent to one ofordinary skill in the art upon reading the foregoing disclosure. Duringsuch a reading it will be evident that this invention provides opticalimaging system for accomplishing the objects and advantages hereinstated.

What is claimed is:

1. An optical imaging system for image exposing a static image on aphotosensitive plate comprising sean ning means for progressivelyscanning a static object at a first speed with a light source;

means for moving a first mirror in parallel in the same direction as thescanning means at a second speed, the plane containing the first mirrorbeing inclined with respect to the plane containing the static image;

means for moving a second mirror in parallel in the same direction assaid first mirror at a third speed, said second mirror facing said firstmirror, the plane containing said second mirror being upwardly directedwith respect to the plane containing said static image so that theoptical length along the path defined by the scanning means, firstmirror and second mirror is substantially constant at all points duringthe movement of said scanning means, first mirror and second mirror;

means for optically focusing the image reflected from said second mirroronto said photosensitive plate;

means for moving said photosensitive plate at a speed relative to saidscanning means;

whereby said imaging system can be compactly arranged because said planecontaining said second mirror is upwardly directed with respect to saidplane containing said static image,

the ratios of the speeds of said scanning means and said first andsecond mirrors being S S, S 1 tan 6, tan (0, 6,):

2l% sin 01 sin (Or-01) +5011 1- 2 C052 9l c0S2 all 't sin 0, sin (O -02)where S said first speed S, said second speed 8, said third speed 0, theangle between the normal to said first mirror and the normal to saidstatic image H the angle between the normal to said second mirror andthe normal to said static image.

1. An optical imaging system for image exposing a static image on aphotosensitive plate comprising scanning means for progressivelyscanning a static object at a first speed with a light source; means formoving a first mirror in parallel in the same direction as the scanningmeans at a second speed, the plane containing the first mirror beinginclined with respect to the plane containing the static image; meansfor moving a second mirror in parallel in the same direction as saidfirst mirror at a third speed, said second mirror facing said firstmirror, the plane containing said second mirror being upwardly directedwith respect to the plane containing said static image so that theoptical length along the path defined by the scanning means, firstmirror and second mirror is substantially constant at all points duringthe movement of said scanning means, first mirror and second mirror;means for optically focusing the image reflected from said second mirroronto said photosensitive plate; means for moving said photosensitiveplate at a speed relative to said scanning means; whereby said imagingsystem can be compactly arranged because said plane containing saidsecond mirror is upwardly directed with respect to said plane containingsaid static image, the ratios of the speeds of said scanning means andsaid first and second mirrors being S0 : S1 : S2 1 - tan theta 1 tan (theta 1 - theta 2):